Air delivery apparatus for air supported structures



D. M. FRAIOLI April 29, 1969 AIR DELIVERY APPARATUS FOR AIR SUPPORTED STRUCTURES Sheet Filed Nov. 2, 1967 INVENTOR DONATO M FRAIOLI %my A GEN T D. M. FRAlOLl 3,440,776

VERY- APPARATUS FOR AIR SUPPORTED STRUCTURES Ap ril 29, 1969 AIR DELI Sheet 2/ of 3 Filed Nov'.

INVENTOR DONATO M FRAIOLI D. M. FRAIOLI A ril 29, 1969 AIR DELIVERY APPARATUS FOR AIR SUPPORTED STRUCTURES Sheet Filed Nov. 2, 1967 INVENTOR DO NATO M. FRAIOLI AGEN United States Patent 3,440,776 AIR DELIVERY APPARATUS FOR AIR SUPPORTED STRUCTURES Donate M. Fraioli, 15 Rowland Ava, Clifton, NJ. 07109 Filed Nov. 2, 1967, Ser. No. 680,212 Int. Cl. E04b 1/34; F16] 5/00 US. Cl. 52-2 6 Claims ABSTRACT OF THE DISCLOSURE through the fabric tube is terminated.

BACKGROUND OF THE INVENTION Field of the invention The present invention relates to air supported structures of the type formed of a shell of flexible sheet material supported by above atmospheric pressure within the structure wherein the pressurizing air is delivered to the interior of the structure through a tube of flexible material.

Description of the prior art Air supported structures of the foregoing type are generally made in the form of hemispheres, or horizontally oriented semi-cylinders, or a combination of these shapes. The walls of such structures are generally vertical where they meet the ground and arch upwardly and inwardly from there. Structures of this type are normally inflated by means of an electrically driven blower positioned on the ground outside of the structure and connected to the structure through an air delivery tube. Two blowers and air delivery tubes are normally provided. Both of these are used to initially inflate the structure and to maintain the pressure in the building during periods when the doors of the building are in use. When the doors of the building are locked, for example during the night, one blower is used to maintain the internal pressure while the second serves as a standby in case of trouble.

In the earlier structures, the air delivery tube was normally of light gauge metal and was positioned parallel with the ground so that it entered an opening in the lower portion of the structure and the air flow was directed along the ground within the structure. This arrangement was found to be unsatisfactory. The drafts created caused discomfort to personnel working in the structure and care had to be taken not to block the opening when storing goods within the structure.

It then became become practice to extend the air delivery tube upwardly at angle of about 45 degrees with the horizontal so that the air entered the structure at a higher portion thereof and was directed toward the ceiling of the structure. This arrangement requires the use of a longer delivery tube which must be supported at one end by the fabric shell of the structure. Because of the weight factor, it became common practice to use fabric air delivery tubes.

The fabric used for the delivery tubes was the same as that used for the shell of the structure, that is, nylon coated with a plastic such as vinyl resin or neoprene. Although the structures had a useful life of ten years or more, the air delivery tubes deteriorated in one year.

3 ,440,776 Patented Apr. 29, 1969 Another disadvantage of air delivery apparatus used in the past was that air within the structure could flow out through a non-operating blower unless manually operated doors at the outlet of the blowers were closed. In the past, it had been found that the need for closing these manually operated doors Wes frequently forgotten when locking the building for the night. As a result the air within the building would rush out through the non-operating blower at a rate greater than could be handled by the one operating blower. Thus, in the morning the building would be completely deflated.

The manually operated blower doors have still another disadvantage. In the event an electrical power interruption occurred, causing the blowers to stop functioning, the air in the building would rush out through the now non-opcrating blowers and allow the structure to collapse in a very short time. Even if personnel were on hand to close the blower doors, a great deal of the internal pressure would be lost before this operation could be completed, and the building could collapse before repairs could be made or an auxiliary power source could be brought into operation.

Still another disadvantage of air delivery apparatus used in the past was that the air inlet openings were completely unobstructed and rubbish such as coffee containers and soda cans were frequently tossed into these openings. This rubbish rolled down the air delivery tube into the blower and in time interferred with or prevented operation of the blower.

SUMMARY Accordingly, an object of the present invention is to provide air delivery apparatus for air supported structures which is not subject to the foregoing difficulty.

Another object is to provide such apparatus which extends the useful life of a fabric air delivery tube.

Another object is to provide such apparatus which minimizes air loss from the structure.

Another object is to provide such apparatus which is protected against clogging and damage.

Another object is to provide such apparatus which directs a quite diffused flow of air into the structure.

Other and further objects of the invention will be obvious upon an understanding of the illustrative embodiment about to be described, or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.

In accordance with the present invention the foregoing objects are generally accomplished by providing improved air delivery apparatus for an air supported structure including a generally arcuate shell formed of flexible sheet material and supported by above atmospheric air pres sure within the structure, the air delivery apparatus comprising in combination means in the shell providing an inlet zone for admitting pressurized air, air pump means positioned outside of the shell, an air delivery tube of a flexible sheet material capable of being adversely effected by vibration during use extending from the air pump means to the inlet zone and terminating at the shell, the outer periphery of the inlet zone being defined by the intersection of the tube and the shell with the tube meeting the shell at an angle so that the inlet zone is of substantially larger area than the cross-sectional area of the tube, the inlet Zone being provided with a plurality of perforations having a total area smaller than the area of the zone to an extent whereby vibration of the tube is prevented.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of the invention has been chosen for the purpose of illustration and description, and

3 is shown in the accompanying drawings, forming a part of the specification, wherein:

FIG. 1 is a partial exterior end view of an air supported structure showing a blower and fabric duct for pressurizing the interior of the structure.

FIG. 2 is a longitudinal sectional view of the portion of the air delivery apparatus present at the junction of the fabric duct and the structure, illustrating the condition of that portion of the apparatus when the blower is not operating.

FIG. 3 is a view taken along the line 33 on FIG. 2 illustrating the perforated inlet zone at the junction of the duct and the structure.

FIG. 4 is a view taken along the line 4-4 on FIG. 2 illustrating the louvered panel at the junction of the duct and the structure.

FIG. 5 is an enlargement view of a portion of FIG. 2 illustrating the manner in which the perforated inlet zone and the louvered panel are stitched together.

FIG. 6 is a view similar to FIG. 2 illustrating the condition of the portion of the junction of the duct and the structure when the blower is operating.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings in detail, there is shown a generally semi-cylindrical structure having generally hemispherical ends and being formed of a thin fabric shell 10 having a radius R and supported by air pressure in the interior of the structure, and an air supply system for maintaining the air pressure within the structure at a value in excess of the ambient atmospheric pressure. The shell is made of plastic coated nylon fabric.

The air supply system normally includes two identical air delivery apparatus positioned side-by-side, only one of which is shown in the drawings. Each air delivery apparatus generally comprises a motor driven blower 11 positioned on the ground outside of the structure, a circular air delivery tube 12 connecting the blower and the structure, a perforated inlet zone 13 in the shell 10, and a louvered panel 14 at the inlet zone 13.

The tube 12 extends from the blower outlet upwardly at an angle of about forty-five degrees with the horizontal to join the fabric shell of the structure at an angle of about thirty degrees. The peripheral line defined by the junction of the tube 12 and the shell 10 is elliptical and defines the outer periphery of the zone 13. The tube is made of the same plastic coated nylon fabric as the shell.

The elliptical perforated zone 13, as best shown in FIG. 3, is provided with a large number of elongated holes or slots 15 arranged in horizontally extending rows.

The louvered panel 14 is made of the same plastic coated nylon fabric as the tube 12 and the shell 10. As best shown in FIG. 4, the panel 14 is formed with an edge portion 16 and an elliptical inner portion 17 which is cut along generally U shaped lines 19 to produce a series of horizontally oriented flaps 20 one above another. Each of these flaps 20 is dimensioned to cover one horizontal row of the slots 15.

Between the shell 10 and the end of the tube 12 there is provided a strain relieving cable 21 positioned within a fabric pocket 22 provided along the periphery of the inlet zone 13. The tube 12, the pocket 22, the shell 10, and the panel 14 are sewn together in a single operation by stitching along lines 24.

The panel 14 is also sewn to the area of the zone 13 by stitching along horizontal lines 25 shown in FIGS. 3, 4, 5 and 6. The stitch lines 25 are positioned between the rows of slots 21 and form hinge lines of the flaps 20 as shown in FIG. 6.

On the inside of the structure, two strips of webbing 26, 27 extend generally vertically along the sides of the flaps 20 of the louvered panel 14. The webbing strips are sewn to the bottom edge of each of the flaps 20 at points 29, and the top and bottom ends of each of these strips are sewn to the shell 10 at points 30 above the panel 14 and points 31 below the panel 14 to cause all of the flaps to move in unison.

In operation, the structure is initially erected by operating both of the blowers to force air through the fabric tubes 12 into the structure. As the pressure within the structure increases, the back pressure on the blowers causes them to slow down. An equilibrium is achieved between the volume of air supplied by the blowers and the volume of air that flows out of the building through the porous fabric, as the pressure within the building reaches about one inch of water (.036 pound per square inch). Each time one of the doors of the building is used, a quantity of air is lost reducing the internal pressure within the building. The blowers then speed up, due to the reduction in back pressure, and the building is quickly brought back to the equilibrium pressure.

In the prior art structure, wherein the air delivery tube met the shell at substantially the same angle, it was discovered that the short life of the tube fabric was due to vibrations or pulsations set up in the tube when the blower was operating.

The vibrations caused the plastic coating on the threads of the nylon fabric to crack and thus expose the nylon fabric to the deteriorating effects of the ultra-violet rays of the sun. It was further discovered that the vibrations in the fabric were caused by oscillations set up in the air flow as it passed from the circular tube through the elliptical opening of substantially larger area into the interior of the structure. The oscillations in the air flow produced pressure oscillations causing the walls of the tube, particularly in the area of the junction of the tube and the shell, to pulsate in and out. After a period of time, this flexing of the tube walls fatigued the plastic coating causing it to crack.

In the air delivery apparatus of the present invention, when the blower 11 is operating the air flows from the tube 12 into the structure through the holes 15 in the perforated zone 13. The perforated zone 13 prevents pulsations in the fabric tube 12 by restricting the rate of flow into the structure from the tube and thereby maintaining the pressure throughout the length of the tube 12 at a value greater than the pressure within the shell 10. The holes 15 in the zone 13 have aggregate area substantially equal to that of the circular tube 12 and the perforated zone 13 acts as a restriction to the flow of air from the tube 12 into the shell, wherefore a substantial pressure is built up in the tube and maintains the walls thereof taut.

While the blower 11 is operating, the air flowing through the holes 15 lift the fabric flaps 20 in the louvered panel 14 as shown in FIG. 6 and air flows freely into the structure. The webbing strips 26 and 27 cause all the flaps 20 to operate in unison to eliminate any tendency which some of the flaps 20 may have to flap noisily.

When the blower 11 is not operating the pressure within the structure is greater than that in the tube 12 and the flaps 20 of the louvered panel 14 are held against the perforated panel (as shown in FIGS. 2, 4, and 5) by the pressure within the structure. The panel 14 thus automatically and effectively seals the slots in the perforated zone 13 to prevent air flow from the interior of the structure through the tube 12 and the blower 11 to the atmosphere.

The presence of the perforated zone 13 and the panel 14 also substantially eliminates the problem of rubbish belng tossed into the air inlet openings from inside the structure.

When the structure is inflated, the shell 10 is tensioned. The cable 21 within the pocket 22 is positioned around the zone 13 to relieve the zone (which is weakened by the slots 15) of the tension forces within the shell.

In a typical building wherein the radius R is thirty feet, the circular tube 12 has a diameter of about three feet, the ellipse formed by the intersection of the tube and the shell extends about six feet along its major axis, the bottom edge of this ellipse is five feet, six inches above ground level, the perforated zone 13 is provided with 195 slots arranged in thirteen rows, the aggregate area of the holes 21 is approximately equal to the crosssectional area of the circular tube 12, the panel 14 is provided with thirteen flaps 20 each of which cover one row of the slots 15.

It will be seen that the present invention provides air delivery apparatus for an air supported structure which greatly extends the useful life of the fabric air delivery tube, minimizes the los of air from the structure, provides a quiet diiiused flow into the structure, and is protected against clogging and damage.

Iclaim:

1. Improved air delivery apparatus for an air supported structure including a generally arcuate shell formed of flexible sheet material and supported by above atmospheric air pressure Within the structure, said air delivery apparatus comprising in combination means in said shell providing an inlet zone for admitting pressurized air, air pump means positioned outside of said shell, an air delivery tube of a flexible material capable of being adversely effected by vibration during use extending from said air pump means to said inlet zone and terminating at said shell, the outer periphery of the inlet zone being defined by the intersection of said tube and said shell, said tube meeting said shell at an angle so that said inlet opening is of substantially larger area than the cross-sectional area of said tube, said inlet zone being provided with a plurality of perforations having a total area smaller than the area of said zone to an extent sufficient to cause a pressure to build up Within the entire length of the tube to prevent vibration of the tube material.

2. Apparaus according to claim 1, wherein said tube is of circular cross-section and said inlet zone is elliptical.

3. Apparatus according to claim 2, wherein said perforations in said inlet zone have a total area about equal to the cross-sectional area of said tube, and means on said inlet zone for-sealing said perforations in response to the pressure within said shell when said blower is not operating.

4. Apparatus according to claim 1, including a fabric panel co-extensive with said inlet zone and positioned against the inner surface of said inlet zone, said panel being cut along lines to form a plurality of movable flaps for covering and sealing said perforations in response to the pressure within said shell when said blower is not operating.

5. Apparatus according to claim 4, wherein said perforations in said inlet zone are arranged in horizontal rows and said panel is stitched to said inlet zone along lines between said rows, said cut lines in said panel being positioned so that said stitching provides hinges at the upper edge of said flaps.

6. Apparatus according to claim 5, including at least one vertically oriented strip extending along the inner surface of said panel and attached to the lower edge of each of said flaps to cause said flaps to operate in unison.

References Cited UNITED STATES PATENTS 2,910,994 11/1959 Joy 522 2,948,286 8/1960 Turner 522 X 3,109,440 11/ 1963 Schjeldahl et al. 52-2 FOREIGN PATENTS 1,192,800 4/1959 France.

965,431 7/ 1964 Great Britain.

FRANK L. ABBOTT, Primary Examiner.

P. C. FAW, JR., Assistant Examiner.

US. Cl. X.R 137357;13840 

